Postcesarean section febrile morbidity remains a common problem on obstetric services. Although a few preliminary studies have reported on the use of ultrasound to assess the postcesarean section patient, they have not compared sonographic findings with either intraoperative or postoperative events. These reports have noted fluid collections around the incision site. In this report of 100 postcesarean section patients, it is noted that echo-free areas anterior to the incision site, which correspond to the described fluid collections, were present in 29% of patients and were more frequently found in patients with excess blood loss surgery. Patients whose echo-free areas were greater than equal to 3.5 cm were significantly more likely to have postoperative morbidity. The significance of these findings and the role of ultrasound in the evaluation of the postcesarean section patient are discussed.